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Question 362437: Bob bought 1 pen and 4 pencils for $1.65. Joe bought 4 pens and 1 pencli for $3.75. How much is a pen
Answer by HasanSahin(52)   (Show Source):
You can put this solution on YOUR website! Let's say pen = A, and pencil = B,
Bob >> A + 4B = $1.65
Joe >> 4A + B = $3.75
You have 2 unknowns and 2 equations. But you must need one unknown and one equation in order to solve this problem.Therefore you must wipe out one variable.For example I want to wipe out A therefore I Multiply the first(Bob's) equation by 4.
It looks like now:
Bob >> 4A + 16B = $6.6
Joe >> 4A + B = $3.75
You have to subtract Joe's equation from Bob's equation in order to wipe out A.
4A + 16B = $6.6
4A + B = $3.75
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0A + 15B = $2.85 Therefore you get 15B = $2.85 and you can find B as $0.19
and if you put B into any equation such as 4A + B = $3.75
you get 4A + $0.19 = $3.75 and when you solve this you get A as $0.89
RF.
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